C6 : Electrolysis Flashcards Preview

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Flashcards in C6 : Electrolysis Deck (14)
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1
Q

What will the electrolysis of AQUEOUS NaCl produce ?

A

Sodium hydroxide
Chlorine
HYDROGEN

2
Q

What happens if metal ions in reaction are lower than H+?

A

Ions lower in reactivity mean EASIER TO DISCHARGE

so that gets discharged instead of H+

3
Q

What ions are discharged easier than OH- ions ?

A

HALIDE IONS (G7)

4
Q

How can IONIC compounds conduct electricity ??

A

Ions can conduct when MOLTEN/AQUEOUS

bc the ions are MOBILE to carry charge

5
Q

What happens to oxygen and aluminium in the electrolysis of aluminium ? Half equations?

A

Oxygen LOSE electrons - gain O2
2O^2- - 4e- —> o2

Aluminium GAINS electrons - lose 02
Al^3+ + 3e- —> Al

6
Q

why is a mixture of cryolite and aluminium oxide used?

A

to lower MP, reducing energy needed to extract aluminium

7
Q

why does the positive electrode have to be replaced at regular intervals? (4)

A
    • electrode is made from carbon
  • 02 is produced at anode (+)
  • reacts with anode to form CO2
  • needs to be replaced, as carbon is being lost
8
Q

why is aluminium expensive

A
  • requires a lot of energy to extract

- requires mining/ getting rid of waste solution

9
Q

why is aluminium formed at the cathode (-)?

A

Al ions are +.
Al ions are attracted to negative electrode.
Al gains electrons and is REDUCED!
Al3+ + 3e- –> Al

10
Q

why does CU2+ form a solid at negative electrode?

A

cu2+ gains 2 electrons to form copper
cu2+ +2e- –» Cu

11
Q

eqn for molten sodium chloride when electrolysed?

A

2NaCl –> 2Na + Cl2

12
Q

equn for molten potassium bromide when electrolysed?

A

2KBr –> 2K + BR2

13
Q

half equation if hydroxide ions are discharged?

A

4OH– ⟶ O2 + 2H2O + 4e–

14
Q

required practical: electrolysis

A
  1. Add the aqueous solution to the beaker
  2. Add two graphite rods as the electrodes/ put test tubes on electrodes and connect this to a power pack or battery
  3. Turn on the power pack or battery and allow electrolysis to take place
  4. Record the results in a suitable table and repeat for another solution, checking the electrodes in between runs to see if any metal has been deposited
  5. The gases produced can be collected in the test tubes to be tested later